3D micromachining of SU-8 polymer with proton microbeam

Proton beam writing system has been developed at the nuclear microprobe of the Ljubljana tandetron laboratory. The system incorporates existing scanning system with the external beam positioning and fast beam switching system. Microstructures are produced according to the digital plan in the B&W bitmap. When the beam passes over the unexposed regions of the digital plan, fast electrostatic deflectors sweep it off. Dose per pixel is controlled either by selecting the irradiation time or by preset number of external counts. To achieve the production of three-dimensional microstructures, two different irradiation energies are applied at the same positions. By the variation of energy and the beam dose various types of three-dimensional structures could be produced. Precise understanding of energy deposition in different layers and dose normalization are essential for regular exposure throughout the polymer. Contrast curve of SU-8 polymer for proton beam irradiation was measured. A selection of optical and SEM images of the resulting micro structures, produced in the SU-8 photo resist, is presented. (c) 2005 Elsevier B.V. All rights reserved.